KR101966318B1 - Sinlge phase pwm converter for high-speed railway propulsion system using discontinuous modulation and method of controlling the same - Google Patents

Abstract

A single phase PWM converter for a high speed railway propulsion control apparatus according to an embodiment of the present invention includes an offset voltage generator for generating an offset voltage based on a converter input command voltage and a clamping voltage output from a current controller; A gate command voltage generator for generating a gate command voltage based on the converter input command voltage and the offset voltage; And a PWM generator generating a PWM signal for controlling the single-phase PWM converter circuit based on the gate command voltage and the carrier wave, wherein the gate command voltage may be a discontinuous modulation waveform.

Description

Single Phase PWM Converter for High Speed Railway Propulsion Control Device Using Discontinuous Modulation Technique and Its Control Method

The present invention relates to a single phase PWM converter for a high speed railway propulsion control device using a discontinuous modulation technique and a control method thereof.

The high-speed railway propulsion control system is largely comprised of a pulse-width modulation (PWM) converter for driving unit power factor control and dc-link constant voltage control, and a PWM inverter for driving a traction motor (FIG. 1). Reference). Among them, the converter uses a full bridge PWM converter capable of bidirectional power conversion during reversal and regeneration, and two interlaced PWM converters to reduce converter input ripple current and share high output. It is composed.

In single-phase PWM converters, the maximum and minimum voltages of the converter input command voltages V _ref (V _UX ^* = V _C ^* / 2, V _VY ^* = -V _C ^* / 2) are always the same, so that the existing carrier based In the switching pattern implemented with sinusoidal PWM (SPWM), the effective voltage is located in the middle of the switching cycle, similar to the space vector modulation method of the three-phase PWM inverter system as shown in FIG. In the existing SPWM method, it can be seen that four switching state changes occur during a switching cycle for a given converter input command voltage V _ref .

Due to the large power system characteristic of hundreds of kW or more, the switching loss is excessive and due to the realistic constraints of the heat dissipation design, the switching frequency is limited to about 9 to 10 times the fundamental frequency (60 Hz) (540 to 600 Hz). On the other hand, when the proportional integral control (PI) is used as the current controller, if the pole of the system and the zero of the controller are adjusted to be the same, the current control system can be controlled relatively stably regardless of the characteristics of the system.

However, since the system closed-loop transfer function appears in the form of a first-order lowpass filter, a delay of the control system inevitably occurs in a system with a low switching frequency, such as a PWM converter for a high speed railway propulsion control device. Therefore, there is a problem that an additional phase compensation technique is required for unit power factor control.

Korean Registered Patent No. 10-1564358 (Invention name: Converter control method and apparatus for current harmonic distortion control at low load conditions)

Accordingly, an object of the present invention is to reduce switching loss by applying a discontinuous modulation technique to a single-phase PWM converter, thereby increasing the frequency band of the high-speed railway propulsion control signal to enable more stable control.

In accordance with an aspect of the present invention, there is provided a single-phase PWM converter for a high speed railway propulsion control apparatus, including: an offset voltage generator configured to generate an offset voltage based on a converter input command voltage and a clamping voltage output from a current controller; A gate command voltage generator for generating a gate command voltage based on the converter input command voltage and the offset voltage; And a PWM generator generating a PWM signal for controlling the single-phase PWM converter circuit based on the gate command voltage and the carrier wave, wherein the gate command voltage may be a discontinuous modulation waveform.

In addition, the control method of the single-phase PWM converter for a high-speed railway propulsion control apparatus according to another embodiment of the present invention comprises the steps of generating an offset voltage based on the converter input command voltage and the clamping voltage; Generating a gate command voltage based on the converter input command voltage and the offset voltage; And generating a PWM signal for controlling the single-phase PWM converter circuit based on the gate command voltage and the carrier wave, wherein the gate command voltage may be a discontinuous modulation waveform.

The present invention relates to a single phase PWM converter for a high speed railway propulsion control device using a discontinuous modulation method and a control method thereof. The band can be increased to allow more stable control.

1 is a diagram illustrating an example of a circuit configuration of a high speed railway propulsion control device.
2 is a diagram illustrating an example of a switching pattern of a conventional continuous modulation method.
3 is a view illustrating a comparison between a switching pattern of a conventional continuous modulation method and a discontinuous modulation method.
4 is a diagram showing the configuration of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.
5 is an operation flowchart illustrating a control method of a single phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.
FIG. 6 is a diagram illustrating voltage waveforms of respective signals in a discontinuous modulation scheme according to an embodiment of the present invention.
7 is a control diagram of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.
8 to 10 are diagrams showing simulation results of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components, unless specifically stated otherwise, one or more other features It is to be understood that the present disclosure does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, parts, or combinations thereof.

The following examples are detailed description to aid in understanding the present invention, and do not limit the scope of the present invention. Therefore, the same range of inventions that perform the same functions as the present invention will also fall within the scope of the present invention.

3 is a view illustrating a comparison between a switching pattern of a conventional continuous modulation method and a discontinuous modulation (DPWM) method.

Referring to FIG. 3, in the case of the conventional continuous modulation method, since both (0,0) and (1,1) are used as zero vectors, a total of four switching state changes occur during a switching cycle, and a discontinuous modulation method is used. In this case, since only (0,0) or (1,1) is used as a zero vector, it can be seen that a total of two switching state changes occur during one switching period.

For example, when only (1,1) is used as a zero vector, the U switch and V switch are clamped to V _dc / 2 alternately during the supply voltage half-cycle, and when only (0,0) is used as the zero vector, The switch and the Y switch are clamped to -V _dc / 2, respectively, so that switching can be suppressed.

In an embodiment of the present invention, an offset voltage technique may be used to form the above-described discontinuous modulation switching pattern.

4 is a diagram showing the configuration of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.

Referring to FIG. 4, a single phase PWM converter using a discontinuous modulation scheme according to an embodiment of the present invention includes a current controller 410, an offset voltage generator 420, a gate command voltage generator 430, and a PWM generator 440. Include.

The current controller 410 is based on a real d-axis current value output from a current coordinate system converter (not shown), a real q-axis current value, and a reference (ref) current value output from a voltage controller (not shown). The input voltage can be output.

The current controller 410 may compare each of the input real d and q-axis current values with a reference current value, pass a proportional integration controller (PI) on the result of the comparison, and perform forward compensation. .

The current coordinate system converter may output a real d-axis current value and a real q-axis current value based on the phase and input current of the power supply voltage, and the voltage controller may output a reference current value based on the reference constant voltage and the real constant voltage.

Here, the current coordinate system converter may include a phase locked circuit (PLL) for phase tracking of the power supply voltage, and the voltage controller may include a proportional integration controller (PI).

The offset voltage generator 420 may generate an offset voltage based on the converter input command voltage and the clamping voltage.

Here, the clamping voltage may be any one of voltages having the magnitude of half the magnitude of the real constant voltage and having opposite signs with respect to the real constant voltage used in the above-described voltage controller.

Here, the offset voltage generator 420 may fix the clamping voltage for the entire period within one period of the converter input command voltage, but may reverse the sign of the clamping voltage for each period of the converter input command voltage. By doing so, the offset voltage generator 420 may allow the period of the offset voltage to be twice the period of the converter input command voltage.

For example, in generating the offset voltage, if a clamping voltage having a positive sign was used in the first period of the converter input command voltage, a clamping voltage having a negative sign may be used in the second period, which is the next period.

In addition, the offset voltage generator 420 may generate an offset voltage based on divided voltages in which the converter input command voltage is divided into two so as to have a magnitude equal to half the magnitude of the converter input command voltage and the signs are opposite to each other.

Here, the offset voltage generator 420 generates the offset voltage by fixing the maximum value or the minimum value of the divided voltages as the reference value for all the sections within one period of the converter input command voltage, but for each period of the converter input command voltage. The maximum value and the minimum value may be alternately used as reference values.

For example, when the reference value is the maximum value, the divided voltage having the larger value of the divided voltages is used as the reference value, and when the reference value is the minimum value, the smaller one of the magnitudes of the divided voltages is determined by the divided voltage having the value. Can be used as a value. Here, since the divided voltages have the form of a sine wave, even when the reference value is fixed to the maximum value, which divided voltage is selected as the reference value may be changed over time.

Here, the timing of sign inversion of the clamping voltage and the timing at which the reference value is changed may be the same.

For example, when the maximum value is fixed to the reference value for all the sections within one period of the converter input command voltage, the clamping voltage is fixed to have a positive sign and for all the sections within one period of the converter input command voltage. When the minimum value is fixed to the reference value, the clamping voltage may be fixed to have a negative sign.

The offset voltage generator 420 may generate an offset voltage by subtracting the reference value from the clamping voltage.

That is, the value at any point of the offset voltage generated by the offset voltage generator 420 is generated based on any one of the clamping voltages and the division voltages, and the offset voltage generated by the above-described process. May generate a gate command voltage having a discontinuous modulation waveform.

The gate command voltage generator 430 generates a gate command voltage based on the converter input command voltage and the offset voltage.

The gate command voltage generator 430 may generate gate command voltages by adding an offset voltage to each of the divided voltages.

This allows the gate command voltage generator 430 to cause the first divided voltage to be clamped to the clamping voltage during the first half period within one period of the converter input command voltage, and the second divided voltage to be clamped to the clamping voltage during the last half period. Can be.

That is, it can be seen that the gate command voltage becomes a discontinuous modulation waveform by the above-described process.

The PWM generator 440 generates a PWM signal for controlling the single phase PWM converter circuit based on the gate command voltage and the carrier wave.

Here, the PWM generator 440 may generate a PWM signal based on the magnitude comparison result of the gate command voltage and the carrier voltage.

Here, the carrier may be a triangular tooth file having a predetermined frequency, but the scope of the present invention is not limited thereto.

In addition, the PWM generator 440 may generate a PWM signal in consideration of a switching dead time.

5 is an operation flowchart illustrating a control method of a single phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.

Referring to FIG. 5, in the control method of a single-phase PWM converter using a discontinuous modulation scheme according to an embodiment of the present invention, the converter input command voltage and the clamping voltage of the offset voltage generator 420 are first output from the current controller 410. Based on the offset voltage is generated (S510).

Next, the gate command voltage generator 430 generates a gate command voltage based on the converter input command voltage and the offset voltage (S520).

Next, the PWM generator 440 generates a PWM signal for controlling the single-phase PWM converter circuit based on the gate command voltage and the carrier wave (S530).

According to the control method of the single-phase PWM converter using the discontinuous modulation technique according to an embodiment of the present invention, a gate command voltage having a discontinuous modulation waveform is generated through steps S510 and S520, and the discontinuous modulation waveform is generated. By using the gate command voltage, a change in the switching state of the PWM signal generated in step S530 may be reduced.

FIG. 6 is a diagram illustrating voltage waveforms of respective signals in a discontinuous modulation scheme according to an embodiment of the present invention.

Referring to FIG. 6, when the converter input command voltage V _ref is given by V _C ^* , the command voltage (the divided voltage on the charge range) is set to 'V _UX ^* = V _c ^* / 2' and 'V _VY ^* = If -V _C ^* / 2 'is set and the maximum voltage V _max and the minimum voltage V _min are obtained from the two command voltages, the offset voltage V _offset may be determined as follows.

To achieve the same conduction and switching characteristics between the switches, V _C ^* 'V _offset = V _dc / 2-V _max ' for one period and 'V _offset = -V _dc / 2-V _min ' for the next period. setting, is clamped to V _C ^* during the half cycle period in the _UX V ^* and V ^* _VY each V _dc / 2 while being clamped to the next V _C ^* half period within a cycle, each -V _dc / 2 to the switching It can be suppressed.

In this case, the extreme voltage may be clamped to V _dc / 2 or -V _dc / 2 in the 180 ° period.

As described above, the process of deriving the leg command voltages V _UX and V _VY according to the offset voltage technique has been described, but the discontinuous modulation technique of the present invention is not limited thereto.

For example, in another embodiment of the discrete modulation scheme of the present invention, a switching pattern as shown in FIG. 6 may be derived through time direct calculation.

As described above, according to the discontinuous modulation scheme of the present invention, since the switching is reduced by half compared to the existing SPWM at the same switching frequency, the switching frequency can be doubled compared to the existing without increasing the switching loss. Therefore, as mentioned above, it is possible to improve the delay and responsiveness of the control system, which is a problem of the PWM converter for the high speed railway propulsion control device having a low switching frequency.

7 is a control diagram of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.

Referring to FIG. 7, a control diagram of a single phase PWM converter using a discontinuous modulation scheme according to an embodiment of the present invention includes a current controller 410, an offset voltage generator 420, a gate command voltage generator 430, and a PWM generator ( 440 is included, and a PLL, a dc-link constant voltage controller, and the like for phase tracking of the power supply voltage may be further included.

The descriptions of the current controller 410, the offset voltage generator 420, the gate command voltage generator 430, and the PWM generator 440 have been described above with reference to FIG.

8 to 10 are diagrams showing simulation results of a single-phase PWM converter using a discontinuous modulation technique according to an embodiment of the present invention.

In particular, FIG. 8 is a diagram illustrating a PSIM simulation result for a 100kW PWM converter for verifying the validity of the proposed discontinuous modulation method.

8 (a) shows the power supply voltage V _S and the input current I _S waveform, and the power factor is 0.999.

8 (b) shows the command voltage V _C1 ^* and the offset voltage V _offset1 . V _offset1 this it can be seen that with alternating V _C1 ^* V every cycle _{dc / 2-V max, -V} dc / 2-V min.

8 (c) shows the command voltages V _UX1 ^* , V _VY1 ^* and the triangular carrier Carrier ₁ to which the offset voltage is added.

FIG. 8 (d) shows leg voltages V _UX1 and V _VY1 as a result of comparing the reference voltages V _UX1 ^* , V _VY1 ^* and the triangular carrier Carrier ₁ , with the two leg voltages alternately V _dc / 2 or -V _dc / It can be seen that it is clamped to 2 and does not switch.

8 (e) shows the converter input voltage V _C1 , and it can be seen that nine switching pulses are generated during a half period, similarly to SPWM (9 pulses).

8 (f) and 8 (g) show the current patterns flowing through the switches. In the non-switching zone, it can be seen that the switch is either completely erased or completely turned on so that switching is suppressed.

According to the DPWM according to an embodiment of the present invention, V _offsets may be alternately controlled to prevent deviations in conduction and switching characteristics of all switches. Therefore, looking at the current waveforms of the switches, it can be seen that they exhibit the same characteristics on average for two cycles of the supply voltage. That is, although the frequency modulation index is increased to 18 times (9 pulses) twice, it can be seen that the switching occurs the same number of times as before.

FIG. 9 illustrates a result of comparing SPWM (9 pulses) and SPWM (18 pulses) in order to confirm a ripple current and a switch loss index of the DPWM according to an embodiment of the present invention.

From the top of each separate first waveform represents the input voltage, input current, and the second waveform is a triangular carrier wave and a reference voltage, and the third waveform of the switch U ₁ current, and the fourth waveform is the channel of the switch U _1, X ₁ (channel ) And the conduction loss of the body diode, the fifth waveform represents the switching loss of the channel and body diode of the switches U ₁ , X ₁ .

The power factor was above 0.99 in all three modulation schemes, with ripple current equal to 34A for DPWM (18 pulses), 37A for SPWM (9 pulses), and 17A for SPWM (18 pulses), which is half that of the other two modulation schemes.

DPWM, a discontinuous modulation scheme according to an embodiment of the present invention, has twice the switching frequency compared to SPWM (9 pulses), but the effective frequency per switching unit cycle is halved due to one leg clamping, resulting in an equivalent level of ripple current. It shows an aspect. Looking at the current behavior of the switch U ₁ SPWM technique is a continuous switching operation every hour and the DPWM is switched only half of the power voltage every cycle (2, 3 in the third waveform of Figure 9 (a) Suppression of section switching). Comparison of conduction losses (P _cond ) shows little difference in all modulation schemes. This is because even though the modulation scheme is different under the same input / output conditions, there is little difference in the aspect of the input current.

Finally, the comparison of switching losses (P _sw ) shows that DPWM (18 pulses) is equivalent to SPWM (9 pulses) and half the SPWM (18 pulses). As a result, the proposed DPWM has the same current ripple and conduction loss as compared to the conventional SPWM (9 pulse), and the switching loss is half that of SPWM (18 pulse).

FIG. 10 shows a result of comparing load regulation according to load variation in control performance. The dynamic characteristics of the dc-link voltage were analyzed when changing from the first 50kW (Half Load) to 100kW (Full Load) and back to 50kW (Half Load).

Since the effective switching frequency of the DPWM has doubled compared to the SPWM, the control bandwidth is set to 500 Hz and 300 Hz, respectively, and the results show that the DPWM reduces the average voltage stabilization time by 58% and the voltage overshoot / undershoot by 80% on the average. Can be.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

410: current controller 420: offset voltage generator
430: gate command voltage generator 440: PWM generator

Claims (10)

In the single-phase PWM converter for high speed railway propulsion control device,
An offset voltage generator for generating an offset voltage based on the converter input command voltage and the clamping voltage output from the current controller;
A gate command voltage generator configured to generate a gate command voltage based on the converter input command voltage and the offset voltage; And
A PWM generator for generating a PWM signal for controlling a single phase PWM converter circuit based on the gate command voltage and the carrier wave;
Including,
The gate command voltage is a discontinuous modulation waveform,
The offset voltage generator
The offset voltage is generated by fixing the clamping voltage for the entire period within one period of the converter input command voltage,
And inverting the sign of the clamping voltage for each period of the converter input command voltage such that the period of the offset voltage is twice the period of the converter input command voltage. delete The method of claim 1,
The offset voltage generator
A single-phase PWM converter using a discontinuous modulation technique, wherein the offset voltage is generated based on the divided voltages of which the converter input command voltage is divided into two so that the converter input command voltage has a magnitude that is half the magnitude of the converter input command voltage. . The method of claim 3, wherein
The offset voltage generator
The offset voltage is generated by fixing a maximum value or a minimum value among the magnitudes of the divided voltages as a reference value for the entire period within one period of the converter input command voltage.
A single-phase PWM converter using a discontinuous modulation technique, wherein the maximum value and the minimum value are alternately used as reference values for each period of the converter input command voltage. The method of claim 4, wherein
The offset voltage generator
When the maximum value is fixed to the reference value for all the sections within one period of the converter input command voltage, the clamping voltage is fixed to have a positive sign,
When the minimum value is fixed to the reference value during the entire period within any one period of the converter input command voltage, the clamping voltage is fixed so as to have a negative sign. . The method of claim 4, wherein
The offset voltage generator
And subtracting the reference value from the clamping voltage to generate the offset voltage. The method of claim 3, wherein
The gate command voltage generator
The offset voltage is added to each of the divided voltages to generate gate command voltages,
Using a discontinuous modulation technique such that a first divided voltage is clamped to the clamping voltage during the first half period within one period of the converter input command voltage and a second divided voltage is clamped to the clamping voltage during the last half period. Single phase PWM converter. The method of claim 1,
The PWM generator
And generating the PWM signal based on the magnitude comparison result of the gate command voltage and the carrier voltage. The method of claim 1,
The PWM generator
Single phase PWM converter using a discontinuous modulation technique to generate the PWM signal in consideration of the switching dead time (dead time). In the control method of the single-phase PWM converter for high speed railway propulsion control device,
Generating an offset voltage based on the converter input command voltage and the clamping voltage;
Generating a gate command voltage based on the converter input command voltage and the offset voltage; And
Generating a PWM signal for controlling a single phase PWM converter circuit based on the gate command voltage and a carrier wave;
Including,
The gate command voltage is a discontinuous modulation waveform,
In the step of generating an offset voltage based on the converter input command voltage and the clamping voltage
Generating the offset voltage by fixing the clamping voltage for the entire period within one period of the converter input command voltage,
And inverting the sign of the clamping voltage for each period of the converter input command voltage such that the period of the offset voltage is twice the period of the converter input command voltage.

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